I want to build an automatic three phase brake

[makenzie71]

I burned up a relay in the night and it took out half a dozen batteries and an inverter...lucky me I use cheap batteries and inverters lol

This is not the first time it's happened, either.

I want to build a device that will automatically short out the three phase leads in the event of another relay failure.  The only way I can see in my head of doing this is with a voltage switch actuated by the battery voltage and two AC/AC relays.  This will cost about $70 in parts per turbine...honestly I only really need it for the two big ones so it's not a huge expense...but I'm not sure if that's the best way to go about it.

What would you guys suggest?

[Astro]

 Tell us more about this relay that fails. Is it a control relay or power relay (do all three phases run through it)? 
What fails? does the coil burn up or does the contacts burn up?
What does the relay do exactly? Is it ac or dc voltage?
That will help to figure out how to answer your question.

[SparWeb]

If you don't trust relays any more, then sadly the thing you're asking about is, yeah you guessed it, another relay.  And the way it works will put a constant trickle load on your battery bank to keep its contacts open.  Any drop in the voltage to this relay's coil will cause its NC contacts to close and there's your short-circuit.  Can you live with that?

[bigrockcandymountain]

A voltage monitoring relay $20 and a couple ice cube relays, $5 will do what you need i think.  I bought one and tested it but never did install it permanently.  It was meant to be a backup to my backup.

The voltage monitoring relay can sense battery voltage or wild ac viltage and be set to latch so it stays shorted once tripped.  The 2 ice cube relays can just be 12v and hooked to part of your battery bank to get 12v. 

The main contacts of the ice cube relays can short ac no problem.   On 2 relays you have 4 main contacts total.  One from each gets hooked to L1 and L2 from the turbine.  The other 2 contacts get hooked together and hooked to L3

That makes a nice 3 phase short when activated.  A 2 pole relay would be more elegant, but they are less common.

Alternatively, you could use a solid state relay instead of a mechanical one in the application that is failing.  They are made to cycle billions of times where mechanical relays are maybe 10 000 times.  I have seen the cheap controllers on ebay and wondered how long the relays would last.

Good to see you still making watts.  Which of your turbines would you recommend the most?

[makenzie71]

Tell us more about this relay that fails. Is it a control relay or power relay (do all three phases run through it)? 
What fails? does the coil burn up or does the contacts burn up?
What does the relay do exactly? Is it ac or dc voltage?
That will help to figure out how to answer your question.

First, I want to be clear here, I'm not looking for solutions for the relays that burn up.  I know why they burn up.  They're cheap Fotek relays that are notoriously unreliable...but I have a stack of them I need to run through before I can move on to better stuff.

What I want is help sorting out a three phase brake.

As to your questions, they're Fotek SSR's that go between the batteries and inverters...and as for why they burn up, well they're Fotek SSR's, it's kind of their thing

[makenzie71]

If you don't trust relays any more, then sadly the thing you're asking about is, yeah you guessed it, another relay.  And the way it works will put a constant trickle load on your battery bank to keep its contacts open.  Any drop in the voltage to this relay's coil will cause its NC contacts to close and there's your short-circuit.  Can you live with that?

It's not about not trusting relays...relays are the only way to do it...I'm just looking for a safety to bring the turbine to a stop should the relays that actually keep it loaded fail.  I'm sure any kind of brake will consume some power while not in operation, that's fine.

A voltage monitoring relay $20 and a couple ice cube relays, $5 will do what you need i think.  I bought one and tested it but never did install it permanently.  It was meant to be a backup to my backup.

The voltage monitoring relay can sense battery voltage or wild ac viltage and be set to latch so it stays shorted once tripped.  The 2 ice cube relays can just be 12v and hooked to part of your battery bank to get 12v. 

The main contacts of the ice cube relays can short ac no problem.   On 2 relays you have 4 main contacts total.  One from each gets hooked to L1 and L2 from the turbine.  The other 2 contacts get hooked together and hooked to L3

That makes a nice 3 phase short when activated.  A 2 pole relay would be more elegant, but they are less common.

Alternatively, you could use a solid state relay instead of a mechanical one in the application that is failing.  They are made to cycle billions of times where mechanical relays are maybe 10 000 times.  I have seen the cheap controllers on ebay and wondered how long the relays would last.

Good to see you still making watts.  Which of your turbines would you recommend the most?

I'm thinking of using two solid state relays and a cheap little voltage switch...voltage gets above something like 65vdc on the high end and the switch hits the relays.  In my head this works but I have a problem getting the things in my head to always work in real life!  I think with an AC SSR, I can run L1 and L2 to the load contacts of SSR#1, L3 and a jumper to SSR#2, with the jumper going back to L2 on SSR#1.  If voltage spikes the controller closes the SSR's and I think that will short all three phases.  The controllers I use have a timer delay on them, also, so I could program it to stop everything for 10 minutes or something if voltage spikes.

I'm not familiar with an ice cube relay?  Could youpossible post a link to one?  My biggest concern with the SSR's is going to be heat.  Bringing my Heli 2.0 down to a stop in full wind generates a lot of heat lol

Oh and yeah I still HIGHLY recommend the iSta Breeze i1500 and i2000.  If you got to buy a turbine off the shelf, look at iSta Breeze.  I'm about to replace the i1500 I've had up for two years so I can switch everything over to 48v...thing still screams and cranks out the power and I've been mean to it lol.  The Heli 2.0 I have up is also a monster but cost different between it (with the upgraded blades that actually let it work) means it's just not as good a return ratio, but definitely an awesome machine.  A couple weeks ago I had a ton of wind and did a whole day measure, you can see how they all performed (or skip to the end and read the graphs )

https://youtu.be/hdS57g6pIxs

[bigrockcandymountain]

Awesome, I'll check out your YouTube.  Every once in awhile someone asks for a recommendation for an off the shelf turbine. 

Ice cube relay is just a 30a or 40a usually 12v relay that is available at every hardware store etc.  They aren't special or anything, just cheap and easy to find.

It sounds like you have a pretty good idea what to do. I would favour a mechanical relay for a short switch over a ssr.  Your amperage goes very high for a few seconds before the blades stop, and i just think mechanical contacts would survive better than a semiconductor device.

A 10 minute delay sounds reasonable.  The relay i have only has latching or no latching for options.  A programmable delay would be better i would think. 

Ill give a plug for VB controls for solid state relays.  A world better than chinese. 
I ordered one for my diversion load.  It came and didn't work right out of the box. They figured high voltage transients damaged it upon startup.  I contacted them, and told them about it.  They asked a bunch of questions about my application and custom built an HD version and shipped it out quickly no charge.  It has been flawless ever since.  Check out VB controls prices.  They aren't super high for the quality you get.

If it was me, i would try a good ssr in place of the fotek.  Not only are you wrecking other components with the cheap relays, there is always the chance of fire or explosion when you wreck batteries.

[Astro]

Tell us more about this relay that fails. Is it a control relay or power relay (do all three phases run through it)? 
What fails? does the coil burn up or does the contacts burn up?
What does the relay do exactly? Is it ac or dc voltage?
That will help to figure out how to answer your question.

First, I want to be clear here, I'm not looking for solutions for the relays that burn up.  I know why they burn up.  They're cheap Fotek relays that are notoriously unreliable...but I have a stack of them I need to run through before I can move on to better stuff.

What I want is help sorting out a three phase brake.

As to your questions, they're Fotek SSR's that go between the batteries and inverters...and as for why they burn up, well they're Fotek SSR's, it's kind of their thing

 And I want to be clear that I do not want to give advice and have it burn someone's stuff down. I mean if a 15 amp fuse is blowing, I am not going to tell someone to put in a 100 amp fuse even though it has #14 wire.
 So knowing why the relay is failing is kind of important.
My guess is you are using to small of a relay. IDK what kind of current you are pulling between battery and inverter, but my guess is that it is more than the relay can handle. SO if the system works otherwise, except when the relay fails, why add anything? Why not just put the right relay/contactor in?
You see why I asked those questions now?
Now that we can skip does this brake system need to be tied into this failing relay (kind of important to know).
Yes, get a adjustable dc voltage relay, sometimes called and over/under voltage relay. Hook it up to the place you want to monitor the voltage (battery voltage). Have it fire a 3 pole relay/contactor when it hits whatever voltage your heart desires. Tap all three phases from the mill, maybe where they connect to the rectifier. run each phase to individual poles of the relay, on the other side of the relay/contactor hook them all together.
Once your battery voltage hits the set point, the battery power will fire the small voltage sensing relay. When it fires it will fire the larger 3 pole relay/contactor and since the other side of those poles are all connected together it will short the mill out. YES you will have a small drain on your batteries to keep said relays fired. Which is why a over/under (or 2 separate voltage sensing relays wired together) is nice, because something has to break the power to the relay/contactor that is now braking the mill, so that the mill can restart and charge the batteries again. AN over/under relay switches according to voltage. So you only need one relay. At the high set point it fires the 3 pole relay/contactor and stays fired until the voltage drops to the lower set point and then it cuts power to the 3 pole relay/contactor and lets the mill restart/
 Sorry if I am crabby this morning, sleep has been hard to come by lately. Good luck with your project.

[Astro]

Tell us more about this relay that fails. Is it a control relay or power relay (do all three phases run through it)? 
What fails? does the coil burn up or does the contacts burn up?
What does the relay do exactly? Is it ac or dc voltage?
That will help to figure out how to answer your question.

First, I want to be clear here, I'm not looking for solutions for the relays that burn up.  I know why they burn up.  They're cheap Fotek relays that are notoriously unreliable...but I have a stack of them I need to run through before I can move on to better stuff.

What I want is help sorting out a three phase brake.

As to your questions, they're Fotek SSR's that go between the batteries and inverters...and as for why they burn up, well they're Fotek SSR's, it's kind of their thing

 And I want to be clear that I do not want to give advice and have it burn someone's stuff down. I mean if a 15 amp fuse is blowing, I am not going to tell someone to put in a 100 amp fuse even though it has #14 wire.
 So knowing why the relay is failing is kind of important.
My guess is you are using to small of a relay. IDK what kind of current you are pulling between battery and inverter, but my guess is that it is more than the relay can handle. SO if the system works otherwise, except when the relay fails, why add anything? Why not just put the right relay/contactor in?
You see why I asked those questions now?
No that we can skip does this brake system need to be tied into this failing relay (kind of important to know).
Yes, get a adjustable dc voltage relay, sometimes called and over/under voltage relay. Hook it up to the place you want to monitor the voltage (battery voltage). Have it fire a 3 pole relay/contactor when it hits whatever voltage your heart desires. Tap all three phases from the mill, maybe where they connect to the rectifier. run each phase to individual poles of the relay, on the other side of the relay/contactor hook them all together.
Once your battery voltage hits the set point, the battery power will fire the small voltage sensing relay. When it fires it will fire the larger 3 pole relay/contactor and since the other side of those poles are all connected together it will short the mill out. YES you will have a small drain on your batteries to keep said relays fired. Which is why a over/under (or 2 separate voltage sensing relays wired together) is nice, because something has to break the power to the relay/contactor that is now braking the mill, so that the mill can restart and charge the batteries again. AN over/under relay switches according to voltage. So you only need one relay. At the high set point it fires the 3 pole relay/contactor and stays fired until the voltage drops to the lower set point and then it cuts power to the 3 pole relay/contactor and lets the mill restart/
 Sorry if I am crabby this morning, sleep has been hard to come by lately. Good luck with your project.

 I should clarify. While an over voltage relay will fire a 3 pole contactor only when over voltage is present and then release it when the voltage falls under that set point and let the mill start again. You could run into a situation where it is constantly switching back and forth, thus shortening the life of the components. A over/under relay gives it a window of acceptable voltage. So say you cut the voltage at 14.4v and short the mill, it will stay fired and keep the mill stalled until it reaches under voltage of say 13.4v. That reduces the cycling of the components and makes them last longer. Basically it stays in the float mode of charging when you set the upper limit at your desired max battery voltage and the lower limit at the voltage where float charge kicks in. Always keeping them pretty well topped off.
 Also make sure to use a 3 pole relay/contactor (and wiring) that can easily handle the amperage of the mill or you will burn the contacts up.

[makenzie71]

I use controllers that have timers on them so it won’t be switching back and forth rapidly.  Once the brake is on, it’ll stay on for 10 minutes or something like that.

[Astro]

I use controllers that have timers on them so it won’t be switching back and forth rapidly.  Once the brake is on, it’ll stay on for 10 minutes or something like that.

Yup that works too. Some kind of latching circuit, be it timed or by voltage will work to keep the relays from chattering.